Agriculture Reference
In-Depth Information
TABLE 16.18
Relationships of C Input, C Buildup, Profile SOC, and C
Sequestration with SYI in a 27-Year Long-Term Experiment
Correlation
Parameters
Regression Equation
(
r
)
(
R
2
)
Annual CR C input (
X
)
SYI (
Y
)
Y
= 0.82
X
- 0.24
0.97
0.94
Total cumulative C input (
X
)
Y
= 0.01
X
+ 0.09
0.93
0.87
C buildup % (
X
)
Y
= 0.02
X
+ 0.11
0.95
0.90
Profile SOC (
X
)
Y
= 0.03
X
- 1.53
0.95
0.90
C sequestrated (
X
)
Y
= 0.03
X
+ 0.29
0.95
0.90
Source:
Srinivasarao, Ch. et al.,
J Plant Nutrition Soil Sci
, doi: 10.1002/jpln.201000429,
2012.
TABLE 16.19
Relationships of SYI to CR C Input, Total Cumulative
C Input, % Change in SOC Stock, and the
Magnitude of SOC Sequestered after 22 Years of
Cropping
Parameters
Regression Equation
R
2
Annual CR C input (
X
)
SYI = 0.16
X
+ 0.30
0.31
Total cumulative C input (
X
)
SYI = 0.001
X
+ 0.39
0.76*
C buildup % (
X
)
SYI = 0.002
X
+ 0.39
0.81*
Profile SOC (
X
)
SYI = 0.004
X
+ 0.2
0.81*
C sequestrated (
X
)
SYI = 0.004
X
+ 0.41
0.81*
Source:
Srinivasarao, Ch. et al.,
Geoderma
, 175-176, 90-97, 2012.
Note:
* Significant at P = 0.05 level.
agronomic productivity of the soybean-safflower system on a long-term basis. Besides
including a legume in sequence, combined use of available organic sources along with
chemical fertilizers might prove beneficial for long-term productivity and sustainabil-
ity of the system (Behera et al. 2007). A significantly higher SYI in soybean has been
obtained by the sole application of chemical fertilizers. This trend is mainly attributed
to resilience of a soil system to intermittent droughts, with high moisture retention
capacity in plots receiving organic amendments compared with those receiving inor-
ganic fertilizers in case of postrainy season crop of safflower. Such a positive response
underlines the importance of organics in enhancing soil resilience under harsh climatic
conditions during the cropping period, a common feature of rainfed agriculture. In
comparison, soybean, being a nutrient-exhaustive (i.e., P) crop, requires more nutrients
during the growing period. Manna et al. (2005) reported a negative yield trend of soy-
bean with unbalanced use of N and NP application in Vertisol.
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